Because audio equipment installed in vehicles are essentially expensive, lightweight and small in size, audio equipment has historically been the subject of much theft. With the thriving aftermarket network, the stolen equipment may be installed in almost any other vehicle.
Automobile manufacturers have employed numerous methods to prevent the audio equipment from being stolen out of the vehicles. For ease of description, the audio equipment will be referred to as a car radio. It is, however, understood that the audio equipment would encompass any sound system installed within an automobile, including cassette tape and compact disc (CD) players.
A variety of prior art approaches have been implemented to deter or prevent theft of such components, including mechanical methods utilizing special security screws to fasten the radio to the vehicle, and electronic methods requiring an operator to insert a special security code to unlock a car radio once the vehicle's battery has cycled. For example, see U.S. Pat. Nos. 4,720,700; 4,743,894; and 4,683,462. Similarly, U.S. Pat. No. 4,808,981 discloses an automotive electronic communication apparatus which prevents the connection of an external battery to a car radio prior to stealing it, in order to prevent an interruption in the power supplied to the car radio.
U.S. Pat. No. 5,870,018 teaches a theft prevention technique wherein a vehicle identification number (VIN) is initially loaded into non-volatile memory of the radio at the factory. Subsequently, upon battery cycling, a currently transmitted VIN on the vehicle's communication bus is compared to the previously stored VIN. If the VINs do not match, the normal operation of the radio is disabled. However, to reinitialize the radio for subsequent operation in a new vehicle, the dealer or service center must reinitialize the new VIN as the authorized VIN using a complex diagnostic system.
There is a need in the art for a component anti-theft arrangement which is both transparent to the vehicle operator and easily overridable by authorized service personnel.